A warhead casing for a penetration-type bomb is designed to penetrate into the ground or into a reinforced structure before the bomb is detonated. As shown in FIG. 1, a known warhead casing 1 typically includes three general regions: a nose region 2, a tubular body region 3, and a tail region 4 opposite the nose region 2. The nose region 2 is generally tapered in an ogive shape and the tubular body and tail regions 3, 4 have generally straight-walled tubular shapes. A payload of explosive material (not shown) is carried by the casing 1, such as within a central cavity 5 enclosed by the casing 1. A fuse 6 is provided for initiating the detonation of the payload of explosive material carried by the bomb, and is typically located in the tail region 4.
Many penetration-type bombs include sensors for sensing environmental conditions so as to determine an appropriate timing for the bomb to detonate. For example, the sensors might include audio sensors, motion or speed sensors, and the like, all of which can provide information relating to the environment of the bomb, which can be relevant to the timing of the explosion of the bomb. For example, the sensors may determine a depth that the casing has penetrated into the ground. The sensor, or power generator, known as the Fusing Unit or FZU, communicate with the fuse such as to activate the fuse or detonator and thereby provide control over when the bomb explodes.
In the known example shown in FIG. 1, such a sensor is positioned in a well or socket 7 formed in the tubular body region 3 approximately half-way between the nose region 2 and the tail region 4 of the casing 1. Such a socket 7 extends through the wall of the tubular body region 3 and into the central cavity 5 of the casing 1. The socket 7 is therefore positioned generally radially outward of the explosive payload in the tubular body region 3, and part-way between the nose region 2 and the tail region 4. A cable 8 extends from the sensor in the socket 7 into the central cavity 5, as shown in FIG. 1. The cable 8 extends rearwardly from the socket 7, through the central cavity 5, toward the tail region 4 to connect with the fuse device 6. Thereby, the sensor may communicate with the fuse 6 through the cable 8.
However, the placement of the sensor socket 7 in the tubular body region 3 renders casing 1, and other known casing designs, vulnerable to premature structural failure when impacting a target. In particular, upon impact with a target and prior to detonation, stresses may concentrate at and around the radially extending sensor socket 7. Consequently, the casing 1 may structurally fail and rupture in the body region 3 near the socket 7 prior to detonation, such that the subsequent explosion pattern is malformed.
Known warhead casings also include an aft closure device, such as aft closure 9, attachable to the tail region for closing the large opening defined by the tail region, and for retaining the fuse in the tail region. As shown in FIG. 1, for example, known aft closures, such as aft closure 9, are approximately the same diameter as the inside diameter of the tubular body region and/or the tail region, and are removably attached to an inner circumference of the casing in the tail region. The aft closure 9 may be attached by threaded engagement and/or held in place by a separate threaded retainer. Additional prior known examples are described in U.S. Pat. No. 6,105,505 and U.S. Pat. No. 5,305,505, the disclosures of which are incorporated herein by reference. Such aft closures are susceptible to premature, unintended detachment from the casing before detonation when the casing impacts a target. In particular, when the nose portion of the casing impacts a target, the casing, including the tail region, may compress axially and simultaneously expand radially. Such radial expansion in the tail region operates to weaken the attachment of the aft closure to tail region. Consequently, the aft closure may disengage from the casing prior to detonation and thereby enable the subsequent explosion to be directed axially outward through the exposed aft opening of the casing rather than primarily radially outward, as is generally desired for penetration-type bombs. Thus, where a radial explosion pattern is desired, the failure of the aft closure attachment results in an undesired, adverse explosion pattern.
Thus, for penetration-type bombs, it is important that the warhead casing remain generally intact after impact with the target and until detonation occurs. As discussed above, structural changes or failures in the casing, such as in the tubular body region or in the tail region with an aft closure device, can adversely affect explosion performance. Accordingly, improvements are needed in the technology areas relating to warhead casings to address the deficiencies of prior known casing designs.